Common Electrical Formulas for DC Circuits

Introduction

• Overview of common electrical formulas encountered in DC circuits.
• Discussion of a simple circuit with a battery and resistor.

Conventional Current and Electron Flow

• Conventional current flows from positive to negative terminal.
• Electron flow is in the opposite direction.

Basic Electrical Formulas

• Ohm's Law: ( V = IR )

  • ( V ): Voltage (volts)
  • ( I ): Current (amps)
  • ( R ): Resistance (ohms)

• Power Formulas:

  • ( P = VI )
  • ( P = I^2R )
  • ( P = \frac{V^2}{R} )
  • Power measured in watts; 1 watt = 1 joule/second

• Electrical Work:

  • Work = Power x Time
  • Energy transfer = Power x Time

Understanding Power and Energy

• Power is the rate of energy transfer.
• 1 horsepower = 746 watts.
• Example: A resistor dissipating 50W converts 50 joules of energy into heat per second.

Calculating Electrical Energy

• Electrical Energy = Charge x Voltage
• Charge (Q) = Current (I) x Time (t)
• Energy = Voltage x Current x Time

Series Circuits

• Current (I) is the same through all components.
• Total Resistance ( R_T = R_1 + R_2 + R_3 )
• Voltage Drop: ( V_1 = I_1R_1, V_2 = I_2R_2, V_3 = I_3R_3 )
• Total Voltage ( V_B = V_1 + V_2 + V_3 ) (Kirchhoff’s Voltage Law)

Parallel Circuits

• Multiple paths for current flow.
• Voltage across each resistor is equal to battery voltage: ( V_B = V_1 = V_2 = V_3 )
• Total Resistance: ( \frac{1}{R_T} = \frac{1}{R_1} + \frac{1}{R_2} + \frac{1}{R_3} )
• Total Current ( I_T = I_1 + I_2 + I_3 ) (Kirchhoff’s Current Law)

Kirchhoff’s Laws

• Voltage Law: Total voltage around any closed loop is zero.
• Current Law: Total current entering a junction equals total current leaving.

Example Problems

• Calculation examples demonstrating Kirchhoff’s Current Law.
• Problem solving approach to determine current direction and magnitude.

Conclusion

• Review of key electrical formulas for DC circuits.
• Encouragement to explore further example problems in additional content.

Additional Resources

• Links to more example problems and related videos available in the description section for further study.